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Modélisation de l'écoulement de la glace dans les calottes polaires : prise en compte d'une loi de comportement anisotrope

Abstract : The ice flows by plastic deformation under gravity, and by sliding over the bedrock, when local temperature is close to the melting point. Mechanical test in laboratory and in-situ deformation measurements have shown the strong viscoplastic annisotropy of deep polar ices. To study the influence of this anisotropy on the flow, we have developped an original and robust numerical model, solving the complet set of mechanical equations. The results show that the anisotropic behaviour of the ice change significantly the flow in polar ice sheets and the datation of ice cores. For isothermal "ice sheets", the surface obtained in the anisotropic case is more flat than in the isotropic case, and shear strain rates are higher and more concentrated at the base of the glacier. The other important result is that the anisotropic ice flow is less sensitive to variations of bedrock topography. The ice is accelerated over bump and is more stagnant in the holes of the relief. In the holes the age of the ice is underestimated by a factor 2 when the anisotropy is not taken into account. Parallel to the complete mode!, we have developped a model based on the shallow ice approximation, that we have formulated for the first time, in the anisotropic case. Comparing the results ofthis model with those obtained with the complete model, we show that the approximation well represents the ice flow over a flat bedrock in the isotropic and anisotropic case, but is not able to de scribe accurately the anisotropic flow over an very irregular bedrock.
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https://tel.archives-ouvertes.fr/tel-00781625
Contributor : Pascale Talour <>
Submitted on : Monday, January 28, 2013 - 9:47:53 AM
Last modification on : Tuesday, December 8, 2020 - 3:42:44 AM
Long-term archiving on: : Saturday, April 1, 2017 - 11:04:23 AM

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  • HAL Id : tel-00781625, version 1

Citation

Anne Mangeney. Modélisation de l'écoulement de la glace dans les calottes polaires : prise en compte d'une loi de comportement anisotrope. Glaciologie. Université Pierre et Marie Curie - Paris VI, 1996. Français. ⟨tel-00781625⟩

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